Lipid therapy in patients with diabetes mellitus - a joint statement by the lipid metabolism commission and the heart and diabetes working group of the German diabetes society (DDG), the diabetes, obesity and metabolism section of the German society for endocrinology (DGE), the heart and diabetes working group of the Germans society for cardiology (DGK) and the joint AG Heart-Hormone-Diabetes of the DGK, DGE and DDG.